This invention relates to digital data readers such as tape readers for reading digital data off punched tape. In numerically controlled machine tools, such tape readers are normally run at approximately 300 characters per second (30 inches per second) and are normally required to be able to stop within one character (0.1 inch) while operating at full speed. This stringent stopping requirement has led to some very sophisticated and expensive tape transports which require much scheduled and unscheduled maintenance and which have relatively short lives. In a typical bi-directional prior art tape reader, the following special tape drive and braking equipment is required in addition to the tape reel drive motors and brakes: two motor driven capstans; two electromagnetic pinch rolls; and two elecromagnetic tape brakes, plus the control circuits and power amplifiers for all of the above.
The principal object of this invention is to simplify such tape readers and significantly reduce their cost by eliminating the necessity for quick stops.
Another object of this invention is to raise the reading speed of such tape readers by eliminating the necessity for quick stops.
A further object of this invention is to improve the reliability of and extend the operating life of such tape readers by eliminating the necessity for quick stops.
An additional object of this invention is to provide a tape reader which can be reversed to re-read a character or characters previously read.
Other objects and advantages of the invention will be apparent from the description which follows.